Marching Orders: The Untold Story of How the American Breaking of the Japanese Secret Codes Led to the Defeat of Nazi Germany and Japan

by Bruce Lee

The most difficult part of the job, according to McCormack, is that “the most astute person, even if an expert on the Far East and possessed of a photographic memory, would derive very few connected impressions—and very little usable information—from merely reading the messages from day to day. They must be pieced together by the most painstaking and laborious process, involving collateral investigation, often of minute points.” By 1943, according to McCormack, the Army has so much information about Japanese shipping to and from Indochina and Thailand that it possesses a good picture of the ships and goods and problems that Japan is having in transporting raw material from the region and sending back the required imports. McCormack’s staff has accomplished this miracle by checking and rechecking decrypts against known Japanese merchant vessels—“high class detective methods”—so the picture is clear and up-to-date. The result is that McCormack’s staff establishes that the Japanese have 450,000 tons of shipping in the South Pacific.